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3 years ago

How can you use Hess’s law to determine a reaction’s enthalpy?

1 answer:

3 0

Hess law is due to enthalpy being a state function, which allows us to calculate the overall change in enthalpy by simply summing up changes for each step of the way, until product is formed. All steps have to proceed at the same temperature and the equations for the individual steps must balance out.

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the diagram below shows DNA molecules. What do the broken lines connected to hydrogen atoms represent in this diagram?

uranmaximum [27]

Answer is: hydrogen bonds.

Hydrogen bond is an electrostatic attraction between two polar groups that occurs when a hydrogen atom (H), covalently bound to a highly electronegative atom such as flourine (F), oxygen (O) and nitrogen (N) atoms.

According to the principle of base pairing hydrogen bonds could form between adenine and thymine (two hydrogen bonds between this nucleobases) and guanine and cytosine (three hydrogen bonds between this nucleobases).

Adenine and guanine are purine derivatives and thymine and cytosine are pyrimidine derivates.

5 0

3 years ago

Read 2 more answers

The equilibrium concentrations of the reactants and products are [HA]=0.280 M, [H+]=4.00×10−4 M, and [A−]=4.00×10−4 M. Calculate

Tems11 [23]

Answer:

6.24

Explanation:

The following data were obtained from the question:

Concentration of HA, [HA] = 0.280 M,

Concentration of H+, [H+] = 4×10¯⁴ M

Concentration of A-, [A−] = 4×10¯⁴ M

pKa =.?

Next, we shall write the balanced equation for the reaction. This is given below:

HA <===> H+ + A-

Next, we shall determine the equilibrium constant Ka for the reaction. This can be obtained as follow:

Equilibrium constant for a reaction is simply the ratio of concentration of the product raised to their coefficient to the concentration of the reactant raised to their coefficient.

The equilibrium constant for the above equation is given below:

Ka = [H+] [A−] /[HA]

Concentration of HA, [HA] = 0.280 M,

Concentration of H+, [H+] = 4×10¯⁴ M

Concentration of A-, [A−] = 4×10¯⁴ M

Equilibrium constant (Ka) =

Ka = (4×10¯⁴ × 4×10¯⁴) / 0.280

Ka = 1.6×10¯⁷/ 0.280

Ka = 5.71×10¯⁷

Therefore, the equilibrium constant for the reaction is 5.71×10¯⁷

Finally, we shall determine the pka for the reaction as follow:

Equilibrium constant, Ka = 5.71×10¯⁷

pKa =?

pKa = – Log Ka

pKa = – Log 5.71×10¯⁷

pKa = 6.24

Therefore, the pka for the reaction is 6.24.

6 0

3 years ago

Mangrove trees are affected by several factors. Which is an abiotic factor contributing to the energy cycle of a mangrove ecosys

kondor19780726 [428]

Answer:

Just think of whats in a forest ecosystem

for example

Water

sunlight

tempreture

4 0

3 years ago

Please help me, I really don't want to fail but I don't know how to do this

Brrunno [24]

Answer:

<u>12 moles</u>

Explanation:

$NH_{3}(g) + O_{2}(g) \: → NO_{2} + H_{2}O(g)$

__↑______↑

8.00 mol | 14.00 mol

________________

$NH_{3}(g) + O_{2}(g) \: → NO_{2} + H_{2}O(g)$

You can turn this into a system of variables which are solvable.

To do this, create variables for the coefficients of each compound in the reaction respectively.

$a(NH_{3}(g)) + b(O_{2}(g)) → \\c(NO_{2}) + d(H_{2}O(g))$

Because to be balanced, the count of atoms in each element of the compound correspond to the coefficient of the variable in that compound so that the count of the left (reactant) side is set equal to the right (product) side.

a corresponds to the coefficient of the first compound, b corresponds to the coefficient of the second compound, c corresponds to the coefficient of the third compound, and d corresponds to the coefficient of the fourth compound.

(Reactant = Product)

Reactant: 1a [N] Product: 1c.

Reactant: 3a [H] Product: 2d.

Reactant: 2b [O] Product: 2c + 1d.

Thus the system is:

1a = 1c

3a = 2d

2b = 2c + 1d.

Then just use the substitution methods to solve.

3 0

2 years ago

PLZ HELP PLZ PLZ ILL MARK AS BRAINLIESTT!!!!

LuckyWell [14K]

Q.1-

Given,

mass - 10grams

volume - 24 cm³

density = mass/volume

density = 10/24

density = 0.416 g/cm³

Q.2-

Given,

mass - 700grams

volume - 1100cm³

density = mass/volume

density = 700/1100

density = 0.6363 g/cm³

5 0

3 years ago